java.awt.event: public class: FocusEvent

java.awt.event
public class: FocusEvent [javadoc | source]

java.lang.Object
   java.util.EventObject
      java.awt.AWTEvent
         java.awt.event.ComponentEvent
            java.awt.event.FocusEvent

All Implemented Interfaces:
Serializable

A low-level event which indicates that a Component has gained or lost the input focus. This low-level event is generated by a Component (such as a TextField). The event is passed to every FocusListener or FocusAdapter object which registered to receive such events using the Component's addFocusListener method. (


FocusAdapter

objects implement the FocusListener interface.) Each such listener object gets this FocusEvent when the event occurs.

There are two levels of focus events: permanent and temporary. Permanent focus change events occur when focus is directly moved from one Component to another, such as through a call to requestFocus() or as the user uses the TAB key to traverse Components. Temporary focus change events occur when focus is temporarily lost for a Component as the indirect result of another operation, such as Window deactivation or a Scrollbar drag. In this case, the original focus state will automatically be restored once that operation is finished, or, for the case of Window deactivation, when the Window is reactivated. Both permanent and temporary focus events are delivered using the FOCUS_GAINED and FOCUS_LOST event ids; the level may be distinguished in the event using the isTemporary() method.

An unspecified behavior will be caused if the {@code id} parameter of any particular {@code FocusEvent} instance is not in the range from {@code FOCUS_FIRST} to {@code FOCUS_LAST}.

Also see:

FocusAdapter

FocusListener

Tutorial: Writing a Focus Listener

author: Carl - Quinn

author: Amy - Fowler

since: 1.1 -

Field Summary
public static final int	FOCUS_FIRST	The first number in the range of ids used for focus events.
public static final int	FOCUS_LAST	The last number in the range of ids used for focus events.
public static final int	FOCUS_GAINED	This event indicates that the Component is now the focus owner.
public static final int	FOCUS_LOST	This event indicates that the Component is no longer the focus owner.
boolean	temporary	A focus event can have two different levels, permanent and temporary. It will be set to true if some operation takes away the focus temporarily and intends on getting it back once the event is completed. Otherwise it will be set to false. Also see: isTemporary serial:
transient Component	opposite	The other Component involved in this focus change. For a FOCUS_GAINED event, this is the Component that lost focus. For a FOCUS_LOST event, this is the Component that gained focus. If this focus change occurs with a native application, a Java application in a different VM, or with no other Component, then the opposite Component is null. Also see: getOppositeComponent since: `1.4` -

Fields inherited from java.awt.event.ComponentEvent:
COMPONENT_FIRST, COMPONENT_LAST, COMPONENT_MOVED, COMPONENT_RESIZED, COMPONENT_SHOWN, COMPONENT_HIDDEN

Fields inherited from java.awt.AWTEvent:
id, consumed, focusManagerIsDispatching, isPosted, COMPONENT_EVENT_MASK, CONTAINER_EVENT_MASK, FOCUS_EVENT_MASK, KEY_EVENT_MASK, MOUSE_EVENT_MASK, MOUSE_MOTION_EVENT_MASK, WINDOW_EVENT_MASK, ACTION_EVENT_MASK, ADJUSTMENT_EVENT_MASK, ITEM_EVENT_MASK, TEXT_EVENT_MASK, INPUT_METHOD_EVENT_MASK, INPUT_METHODS_ENABLED_MASK, PAINT_EVENT_MASK, INVOCATION_EVENT_MASK, HIERARCHY_EVENT_MASK, HIERARCHY_BOUNDS_EVENT_MASK, MOUSE_WHEEL_EVENT_MASK, WINDOW_STATE_EVENT_MASK, WINDOW_FOCUS_EVENT_MASK, RESERVED_ID_MAX

Fields inherited from java.awt.AWTEvent:

id, consumed, focusManagerIsDispatching, isPosted, COMPONENT_EVENT_MASK, CONTAINER_EVENT_MASK, FOCUS_EVENT_MASK, KEY_EVENT_MASK, MOUSE_EVENT_MASK, MOUSE_MOTION_EVENT_MASK, WINDOW_EVENT_MASK, ACTION_EVENT_MASK, ADJUSTMENT_EVENT_MASK, ITEM_EVENT_MASK, TEXT_EVENT_MASK, INPUT_METHOD_EVENT_MASK, INPUT_METHODS_ENABLED_MASK, PAINT_EVENT_MASK, INVOCATION_EVENT_MASK, HIERARCHY_EVENT_MASK, HIERARCHY_BOUNDS_EVENT_MASK, MOUSE_WHEEL_EVENT_MASK, WINDOW_STATE_EVENT_MASK, WINDOW_FOCUS_EVENT_MASK, RESERVED_ID_MAX

Fields inherited from java.util.EventObject:
source

Constructor:

Constructor:
public FocusEvent(Component source, int id) { this(source, id, false); } Constructs a `FocusEvent` object and identifies it as a permanent change in focus. This method throws an `IllegalArgumentException` if `source` is `null`. Parameters: `source` - The `Component` that originated the event `id` - An integer indicating the type of event. For information on allowable values, see the class description for FocusEvent Throws: `IllegalArgumentException` - if `source` equals {@code null} Also see: getSource() getID()
public FocusEvent(Component source, int id, boolean temporary) { this(source, id, temporary, null); } Constructs a `FocusEvent` object and identifies whether or not the change is temporary. This method throws an `IllegalArgumentException` if `source` is `null`. Parameters: `source` - The `Component` that originated the event `id` - An integer indicating the type of event. For information on allowable values, see the class description for FocusEvent `temporary` - Equals `true` if the focus change is temporary; `false` otherwise Throws: `IllegalArgumentException` - if `source` equals {@code null} Also see: getSource() getID() isTemporary()
public FocusEvent(Component source, int id, boolean temporary, Component opposite) { super(source, id); this.temporary = temporary; this.opposite = opposite; } Constructs a `FocusEvent` object with the specified temporary state and opposite `Component`. The opposite `Component` is the other `Component` involved in this focus change. For a `FOCUS_GAINED` event, this is the `Component` that lost focus. For a `FOCUS_LOST` event, this is the `Component` that gained focus. If this focus change occurs with a native application, with a Java application in a different VM, or with no other `Component`, then the opposite `Component` is `null`. This method throws an `IllegalArgumentException` if `source` is `null`. Parameters: `source` - The `Component` that originated the event `id` - An integer indicating the type of event. For information on allowable values, see the class description for FocusEvent `temporary` - Equals `true` if the focus change is temporary; `false` otherwise `opposite` - The other Component involved in the focus change, or `null` Throws: `IllegalArgumentException` - if `source` equals {@code null} Also see: getSource() getID() isTemporary() getOppositeComponent() since: `1.4` -

 public FocusEvent(Component source,
    int id) {
        this(source, id, false);
}

FocusEvent

This method throws an IllegalArgumentException if source is null.

Parameters:

source - The Component that originated the event

id - An integer indicating the type of event. For information on allowable values, see the class description for FocusEvent

Throws:

IllegalArgumentException - if source equals {@code null}

Also see:

getSource()

getID()

 public FocusEvent(Component source,
    int id,
    boolean temporary) {
        this(source, id, temporary, null);
}

FocusEvent

This method throws an IllegalArgumentException if source is null.

Parameters:

source - The Component that originated the event

id - An integer indicating the type of event. For information on allowable values, see the class description for FocusEvent

temporary - Equals true if the focus change is temporary; false otherwise

Throws:

IllegalArgumentException - if source equals {@code null}

Also see:

getSource()

getID()

isTemporary()

 public FocusEvent(Component source,
    int id,
    boolean temporary,
    Component opposite) {
        super(source, id);
        this.temporary = temporary;
        this.opposite = opposite;
}

FocusEvent

Component

FOCUS_GAINED

Component

FOCUS_LOST

Component

null

This method throws an IllegalArgumentException if source is null.

Parameters:

source - The Component that originated the event

id - An integer indicating the type of event. For information on allowable values, see the class description for FocusEvent

temporary - Equals true if the focus change is temporary; false otherwise

opposite - The other Component involved in the focus change, or null

Throws:

IllegalArgumentException - if source equals {@code null}

Also see:

getSource()

getID()

isTemporary()

getOppositeComponent()

since: 1.4 -

Method from java.awt.event.FocusEvent Summary:
getOppositeComponent, isTemporary, paramString

Methods from java.awt.event.ComponentEvent:
getComponent, paramString

Methods from java.awt.AWTEvent:
consume, convertToOld, copyPrivateDataInto, dispatched, getAccessControlContext, getID, isConsumed, paramString, setSource, toString

Methods from java.util.EventObject:
getSource, toString

Methods from java.lang.Object:
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method from java.awt.event.FocusEvent Detail:
public Component getOppositeComponent() { if (opposite == null) { return null; } return (SunToolkit.targetToAppContext(opposite) == AppContext.getAppContext()) ? opposite : null; } Returns the other Component involved in this focus change. For a FOCUS_GAINED event, this is the Component that lost focus. For a FOCUS_LOST event, this is the Component that gained focus. If this focus change occurs with a native application, with a Java application in a different VM or context, or with no other Component, then null is returned.
public boolean isTemporary() { return temporary; } Identifies the focus change event as temporary or permanent.
public String paramString() { String typeStr; switch(id) { case FOCUS_GAINED: typeStr = "FOCUS_GAINED"; break; case FOCUS_LOST: typeStr = "FOCUS_LOST"; break; default: typeStr = "unknown type"; } return typeStr + (temporary ? ",temporary" : ",permanent") + ",opposite=" + getOppositeComponent(); } Returns a parameter string identifying this event. This method is useful for event-logging and for debugging.

Method from java.awt.event.FocusEvent Detail:

 public Component getOppositeComponent() {
        if (opposite == null) {
            return null;
        }
        return (SunToolkit.targetToAppContext(opposite) ==
                AppContext.getAppContext())
            ? opposite
            : null;
}

Returns the other Component involved in this focus change. For a FOCUS_GAINED event, this is the Component that lost focus. For a FOCUS_LOST event, this is the Component that gained focus. If this focus change occurs with a native application, with a Java application in a different VM or context, or with no other Component, then null is returned.

 public boolean isTemporary() {
        return temporary;
}

Identifies the focus change event as temporary or permanent.

 public String paramString() {
        String typeStr;
        switch(id) {
          case FOCUS_GAINED:
              typeStr = "FOCUS_GAINED";
              break;
          case FOCUS_LOST:
              typeStr = "FOCUS_LOST";
              break;
          default:
              typeStr = "unknown type";
        }
        return typeStr + (temporary ? ",temporary" : ",permanent") +
            ",opposite=" + getOppositeComponent();
}

Returns a parameter string identifying this event. This method is useful for event-logging and for debugging.